The invention relates to an artificial tooth that contains polymethacrylate, barium aluminum silicate glass and microfine silicon dioxide.
Ceramic teeth and plastic (resin) teeth are used to produce tooth prostheses.
Plastic (resin) teeth that are based on polymethacrylate resins are well-known. These can be prepared by polymerization of mixtures of polymeric and monomeric methyl methacrylate and optionally methacrylic acid esters with multivalent alcohols acting as cross-linking agents by the so-called powder/liquid process (R. Marxkors and H. Meiners, Taschenbuch der zahn arztlichen Werkstoffkunde [Handbook of Dental Materials], First Edition, 1978, Carl Hanser Verlag, Munich, 91).
German Patent Disclosure DE 2 312 258 A discloses abrasion-proof, polishable materials and artificial teeth made from them, comprising a polymer matrix and fine-particle inorganic filler (macrofiller) dispersed in it. The filler comprises glass and/or ceramic with a minimum size of 0.8 to 8 micrometers and a maximum size of 3 to 20 micrometers. To form the polymer matrix by the powder/liquid process, powdered homo- and copolymers of methacrylic ester, and liquid monomers, such as methyl methacrylate, butyl acrylate, polyethylene glycol dimethacrylate and bisphenol-A-dimethacrylate, are used.
German Patent DE 24 62 271 C describes molded dental elements, especially artificial teeth and tooth replacement elements, that comprise polymers of acrylate or methacrylate and microfine silicon dioxide (microfillers). The microfine silicon dioxide, with a particle size of from 10 to 400 nanometers, is silanized, for instance by treatment with 3-methacryloyloxypropyltrimethoxysilane, and may be contained in the molded elements in an amount of 20 to 80 weight %. However, it has been found that plastic teeth that contain microfine silicon dioxide have a tendency to accumulate plaque. Moreover, they are not adequately resistant to compressive strain; as a result, crazing occurs, which causes discoloration and premature abrasion, and the teeth can break.
German Patent DE 24 05 578 C discloses preparing at least the outer layer of artificial teeth from a material that in addition to esters of methacrylic acid contains from 30 to 80 weight % of an inorganic filler comprising a mixture of amorphous silicic acid, produced by flame hydrolysis, and fine-particle glass, such as barium aluminum silicate glass. The proportion of this glass may make up to 25 weight % of the filler mixture.
German Patent DE 38 26 233 C proposes a composite tooth replacement element for the provision of crowns and bridges and for inlays and the like, comprising a core with high bending strength and a high modulus of elasticity, and an abrasion-proof jacket with a high-gloss surface. The core and the jacket comprise acrylate or methacrylate polymer and inorganic filler, and the filler in the case of the core can comprise 80 to 90 weight % barium aluminum silicate glass with a mean particle size of from 0.7 to 10 micrometers and from 10 to 20 weight % of highly dispersed silicon dioxide with a mean particle size of from 0.01 to 0.4 micrometers. The core contains from 30 to 90 weight % of the filler. The plastic of the core and the jacket is preferably a polymer of bis-(4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl)dimethylmethane (so-called bis-GMA or Bowen monomer, U.S. Pat. No. 3,066,112 to Bowen), ethoxylated bisphenol-A-diacrylate, ethoxylated bisphenol-A-dimethacrylate, triethylene glycol dimethacrylate, dodecandiol dimethacrylate, urethane dimethacrylate from 2-hydroxyethyl methacrylate and 2,2,4-trimethylhexamethylene diisocyanate, bis-(acryloyloxymethyl)tricyclo(5,2,1,0.sup.2,6)decane and/or bis-(methacryloyloxymethyl)tricyclo(5,2,1,0.sup.2,6)decane.
German Patent Disclosure DE 40 29 230 A relates to a dental material based on polymerizable monomers as a binder, which contain from 20 to 90 weight % of a filler mixture of amorphous beadlike silicon dioxide particles and up to 20 mol % of an oxide of at least one element of groups I, II, III and IV with a mean primary particle size of from 0.1 to 1.0 micrometers; powdered quartz, glass ceramic or glass having a mean particle size of 0.5 to 5.0 micrometers; and optionally a microfiller for adjusting the viscosity. The addition of dibenzoyl peroxide, for example, to this dental material produces a hot-polymerizable material for making inlays and artificial teeth. The transparency and polishability are considered to be quite good.
A dental material that contains both conventional inorganic fillers (macrofillers) and microfine inorganic fillers--for which the term "hybrid composite" has come to be conventionally used--is described for example in International Patent Application WO 81/02254. It contains a filler mixture of hydrophobic silicon dioxide, with a diameter of from 0.01 to 0.04 microns, and glass, such as radiopaque glass containing barium or strontium, with a diameter of 2 to 30 microns. Bis-GMA or ethoxylated bisphenol-A-dimethacrylate and triethylene glycol dimethacrylate serve as the polymerizable monomers. The material is used as a tooth filling material and for veneering gold crowns, made for example by casting.
A dental material curable by photopolymerization is known from German Patent Disclosure DE 41 10 612 A; it essentially comprises from 10 to 60 weight % bis-(4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl)dimethylmethane, triethy lene glycol dimethacrylate and/or the diurethane dimethacrylate of 2,2,4-trimethylhexamethylene diisocyanate and 2-hydroxyethyl methacrylate, from 37 to 87 weight % of a filler mixture comprising from 80 to 90 weight % barium aluminum silicate glass, with a mean particle size of 0.5 to 1.5 micrometers, and 10 to 20 weight % microfine silicon dioxide, with a mean particle size of from 0.04 to 0.06 micrometers, from 0.02 to 2 weight % .alpha.-diketone, and 0.1 to 1 weight % amine. From this dental material, radiopaque abrasion-proof tooth fillings and inlays that can be polished to a high gloss can be prepared.